\section{Experiments}
In this section the experiments and the experimental setup will be introduced.
\subsection{Experimental Setup}
The experiments are performed in the RobWorkStudio in a empty free-floating environment, meaning that no outer forces acts on the object. The only forces and torques that act on the object, is from the gripper. In figure \ref{fig:gripper:1} the two finger jaw gripper is presented with its embedded coordinate frame. In figure \ref{fig:gripper:2} the object to be grasped are presented together with the gripper. The object is a piece of a modular plastic construction beam, with a mass of 0.372 kg. The fingers are rubber, and the friction coefficient between the gripper and the object is as default set to 0.2. The friction coefficient is in a series of experiments varied to investigate its influence on the wrench space measure. The force the gripper exerts on the object has a maximum 50N of per finger.
\begin{figure}[H]
\subfigure[]{\includegraphics[width=0.49\textwidth]{figures/gripper2.png}\label{fig:gripper:1}}
\subfigure[]{\includegraphics[width=0.49\textwidth]{figures/gripper.png}\label{fig:gripper:2}}
\caption{Figure \ref{fig:gripper:1} showing the gripper used in the experiment with the corresponding frame, red being the x-axis, green y-axis and blue the z-axis. Figure \ref{fig:gripper:2} showing the used gripper and the grasped object.}
\label{fig:gripper}
\end{figure}

\subsection{Post Grasp Evaluation}
Given a proposed grasp that has successfully grasped the object in a free-floating environment, we want to further investigate how good the grasp is by a post evaluation. This post evaluation should ensure that the grasps are able to withstand an outer force e.g. gravity or a movement of the gripper with an object. Directly related to those one could apply gravity or make a move with the gripper. This is however not suitable in this particular context as the objective is to evaluate quality measures rather than a single grasp.\\
Because of this we want a thorough evaluation of each grasp such that correlation between the quality measures and the grasp outcome is exposed. Ideally this means that we want to apply a known force in "all" directions such that we ensure that the grasp is able to withstand this force. This however is a bit cumbersome due to computational reasons which is why we apply a known force in six directions namely the positive and negative direction of the three main axes x, y and z of the gripper frame. Hereby the minimum number of directions is covered. The gripper frame is chosen as reference such that potential gripper specific properties will be exploited in the results.\\
\noindent
The reason why the post evaluation is limited to six directions is that for each direction we need to perform a full grasp simulation to ensure that the starting condition for each of the directions are similar. This results in seven grasp simulation for each successful grasp in free-floating mode, and for each extra direction another simulation will be needed to be carried out.\\
\clearpage
\noindent The need for individual simulation is explained by the following problem. If an object slips when evaluated in one direction and still are kept, the contact points has most likely changed and hence the corresponding quality measure has changed, which means that when evaluating the next direction a different quality measure is evaluated, which of course is a problem.

\subsection{Experimental Procedure}
The sequence for evaluation of the grasps are as follows:
\begin{verbatim}
A scene is loaded with gripper and object
2.000 potential grasps are generated
for each grasp
  Simulate grasp in free-floating environment
  Flag as successful grasp if successful
end
for each successful grasp
 for each testing Directions (XYZ positive and negative)
  Simulate grasp
  Apply force in Direction
  Verify that object is kept
 end
end 
\end{verbatim}
